The present invention relates in general to a wireless power transmission system. One particular aspect of the present invention relates to a remote power transmission system for recharging electronic equipment.
Millions of portable electronic devices are in use today. Each of these devices typically employs a rechargeable battery pack that requires periodic connection to a charger. Many simply forget to connect the equipment to the charger and are left without sufficient power to use their portable electronics. Frequently, the portable electronic equipment is being used in locations where an outlet for the charger is simply not available. The present invention relates to a system for wirelessly delivering electrical power to portable electronic devices.
Wireless power transmission is defined as a point-to-point energy or power transmission through free space (a vacuum), the atmosphere, or other media without the use of conductors. Attenuation of the energy from the transmitter to the receiver is not a function of the distance that separates them unless the medium through which the energy travels affects the energy. For example, in a perfect vacuum, the power beam would travel indefinitely, no matter the distance. This can also be referred to as a conductorless power transmission. This is contrary to an induction system, for example, which must have a minimum to zero distance between the induction coils in order to function.
Originally, a conductorless power transmission system was proposed to augment the existing system of electrical conductors that are used to move large quantities of electrical power over long distances. Later, systems were proposed to convert large quantities of solar energy into an energy beam that could be transmitted from outer space to the surface of the earth through satellite transmissions. Once on earth the energy beam would be converted back to a usable energy form that would be pumped into the existing electrical energy distribution grid. See for instance U.S. Pat. Nos. 3,114,517; 3,781,647; and 3,174,705. Several transmission frequencies of the energy spectrum have been considered to minimize the energy loss from the beam as it travels through the atmosphere, including radio frequency (RF), laser, and optical frequency (OF). For the RF energy beam, atmospheric attenuation is a minimum up to 4 GHz even during a heavy rainstorm. Other windows of transmission exist at 35 GHz and 94 GHz. Systems designed to operate at these relatively high frequencies have the added advantage of operating at smaller apertures wherein the transmitting antenna and the receiving antenna can be smaller. Such systems have been considered for transmission of energy from satellites in a low earth orbit or geosynchronous orbit to the surface of the earth, a distance of many kilometers. Transmitting from space to the surface of the earth greatly diminishes laser based energy beam capabilities due to the long distances the laser beam must travel in the earth's atmosphere.
A wireless remote system capable of transmitting energy distances of 100 to 500 meters typically is all that is needed. At these relatively short distances, even taking into account additional power requirements for attenuation in the earth's atmosphere, many more RF bands become available. Energy transmission via a laser beam also becomes viable. Laser energy beam transmission has the additional advantage of requiring relatively small transmitting and receiving antennae.